The present invention relates to building siding panels, particularly those made from thermoplastic "vinyl" materials such as polyvinylchloride (PVC) that are extruded into a predetermined shape and size. In securing vinyl siding to walls of residential or commercial building structures, installers must often take into account the inherent expansion and contraction properties of the material used when that material is subjected to temperature fluctuations. It has become understood that when the siding is secured flush to a wall with nails, staples or other fasteners, the natural expansion and contraction of the vinyl material is impeded, thereby resulting in an unsightly rippling distortion commonly known as "oil-canning." With conventional siding, in order to prevent the oil-canning effect, the installer must allow for a slight clearance between the fastener (e.g. nail) head and the portion of the siding (i.e. nailing hem) through which the fastener extends in securing the panel to the wall. This is often difficult to achieve given the ease by which fasteners are driven too tightly, even by professional siding installers. In other conventional siding structures where fastening is achieved by staples, installers resort to installing one staple leg into a nail slot in the body of the siding, while the other staple leg is driven over an edge of the siding nail hem into a wall. Those structures similarly are disadvantageous since driving the staple over the nailing hem often results in flush fastening of the staple to the wall, the hem (or both), and the accompanying oil-canning problem described above. That installation also results in uneven fastening. Alternatively, the installer to avoid flush fastening undesirably drives the staple in at an angle which often results in either an insecure installation, oil-canning, or both.
There have been a number of structures described that attempt to overcome the inherent oil-canning distortion that accompanies the use of thermoplastic materials for siding. For example U.S. Pat. No. 4,102,106 discloses the use of parallel ridges on the surface of the nailing hem portion of the siding to prevent a nail from being driven flush with the hem. U.S. Pat. No. 4,617,774 illustrates the use of a removable protrusion to combat oil-canning that acts as a spacer between adjacent panels during installation and once removed enables free movement between the interlocking panels that have been exposed to weather changes. Guide ribs on the surface of the nailing hem are also disclosed to guide a nail which secures the panel. Similarly, U.S. Pat. No. 4,580,383 describes a stop on a locking strip that may be fractured to allow movement between adjacent panels in the event of thermal expansion. U.S. Pat. No. 5,224,318 describes longitudinally aligned and horizontally elongated mounting slots having a vertical length that is wider than the shank of a nail yet narrower than the nail head to prevent flush (tight) fastening. Each slot is placed in a recessed region between two flat ridges that prevent a hammer head from entering the region and thereby avoids flush fastening. Likewise, U.S. Pat. Nos. 4,669,238, 4,930,287, 4,435,938, and 5,535,567 show a series of longitudinally aligned horizontally elongated slots in a recessed section to accommodate and relieve thermal expansion and contraction of the panels. U.S. Pat. Nos. 4,186,538, 4,348,849, 4,930,287, and 4,450,665 similarly use longitudinally aligned elongated slots.
U.S. Pat. Nos 4,731,917 and 4,187,589 disclose the use of staples to fasten the siding, with one staple leg being driven beyond the edge of the siding while the other staple leg extends through a slot in the siding.
U.S. Pat. No. 5,016,415 describes a panel strip having a number of rows of longitudinally aligned horizontally elongated slots. U.S. Pat. No. 5,490,359 fastens siding to a metal building using a screw that is placed through flanges.
While the foregoing references describe various assemblies that are said to minimize oil-canning, they do not provide, a relatively inexpensive and readily extruded assembly that may be installed uniformly and quickly using a staple gun without concern that the staples will provide an uneven, insecure or overly tight installation.
It is an object of the present invention to provide an improved extruded thermoplastic siding panel that may be readily and uniformly fastened along with interlocking adjacent panels to a building structure in a manner that minimizes the oil-canning that results from thermal expansion and/or contraction of the panel.
It is a further object of the present invention to provide such a panel which may be installed with either nails or staples without the conventional disadvantages that have accompanied either fastening method.
In accordance with the present invention, a siding panel to be attached to a building substrate is provided with a hem attaching portion near the upper end of the panel body, said hem attaching portion being generally parallel to the wall, and having a plurality of horizontally spaced-apart slot pairs, each such pair comprising an upper slot and a lower slot that are vertically aligned and spaced apart in relation to each other. The siding is fastened to the substrate using fasteners that are driven into each slot. When staples are used as the fastener, each of the two staple legs extend through the upper and lower slots of a slot pair, respectively. Extending upwardly from the hem portion is a C-shaped curl section having a vertically oriented flat edge that is generally parallel to both the hem attaching portion and the substrate and spaced part from the substrate. The C-shaped portion serves as a guide for the fastening means and prevents fasteners from being driven flush, or at an angle into the slots. Adjacent panels interlock using conventional locking assemblies wherein a flange portion near the lower end of a panel engages a generally U-shaped portion that may be below the hem portion of an adjacent panel.